A proposal has been made on a steering column system including: a jacket configured to rotatably support a steering shaft; a lock mechanism configured to adjust this jacket in the longitudinal direction and in tilt; a breakable member configured to enable the jacket to move in its axial direction when an excessive impact force in excess of a predetermined value is applied to the jacket (see Patent Literature 1, for instance).
As shown in FIG. 1, this steering column system 100 includes: a steering shaft 101 having a steering wheel (not illustrated) fixed to an axially uppermost end; a jacket 102 configured to rotatably support this steering shaft 101; a guide member 103 configured to guide this jacket 102; and a lock mechanism 104 configured to lock the jacket 102 to the guide member 103. The lock mechanism 104 chiefly includes: paired tooth part 105 and tooth part 106, the tooth part 106 provided in the inside of the jacket 102 and the tooth part 105 provided in a telescopic long hole 110 of the jacket 102; a clamp member 108 including a bolt 107 whose head portion 107a is connected to the moving-side tooth part 106; and an operation lever 109 for operating this clamp member 108. The bolt 107 has a neck portion 107b situated between the jacket 102 and the guide member 103.
In the case of the foregoing configuration, once the operation lever 109 is rotated in an unlocking direction, the bolt 107 moves toward the steering shaft 101, and the paired tooth parts 105 and 106 are accordingly unmeshed from each other. This makes the jacket 102 capable of moving in its axial direction. On the contrary, once the operation lever 109 is rotated in a locking direction, the bolt 107 moves in a direction away from the steering shaft 101, and the paired tooth parts 105 and 106 accordingly mesh together. For this reason, the jacket 102 is locked to the guide member 103, and is accordingly inhibited from moving in its axial direction. At this time, if an excessive axial impact force in excess of a predetermined value is applied to the jacket 102 through the steering shaft 101 due to reasons such that a driver is hit against the steering wheel in a vehicle collision, the bolt 107 receives a shearing force, and accordingly breaks at the neck portion 107b. Thus, the head portion 107a is detached from the bolt 107. This makes the steering shaft 101 and the jacket 102 capable of moving in their axial directions.
Another steering column system 120, which is shown in FIG. 2 includes: paired separable members 121, 122; a moving-side tooth part 106 provided in the separable member 121; a fixed-side tooth part 105 provided in a telescopic long hole 110; and a shear pin 123 which extends along the bolt 107, and which connects the separable members 121, 122.
In the case of the foregoing configuration, if an excessive axial impact force in excess of a predetermined value is applied to the jacket 102 through the steering shaft 101 while the jacket 102 is being locked by the paired tooth parts 105 and 106 being in mesh, the shear pin 123 breaks due to the shearing force. Accordingly, the separable member 121 is detached from the separable member 122. This makes the steering shaft 101 and the jacket 102 capable of moving in their axial directions.
[Citation List]
[Patent Literature]
Patent Literature 1: Japanese Patent Application Laid-Open No. Hei.-10-157634.